Generally, a wind turbine includes a tower, a nacelle mounted on the tower, and a rotor coupled to the nacelle. The rotor typically includes a rotatable hub and a plurality of rotor blades coupled to and extending outwardly from the hub. Each rotor blade may be spaced about the hub so as to facilitate rotating the rotor to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy.
To properly orient the rotor blades relative to the direction of the wind, wind turbines typically include one or more yaw drive mechanisms configured to engage a single yaw bearing for rotating the nacelle relative to the tower. As wind turbines continue to increase in size, this yaw bearing must similarly increase in size. However, a yaw bearing of such increased size may be impractical and/or disproportionately expensive. For example, the yaw bearing of a larger wind turbine may be subjected to increased loading. In order for the yaw bearing to withstand such loading, it must include various components that can adequately react the increased loads. Thus, for example, two, three, or more rows of bearing balls may be included in a yaw bearing. However, such increase in the number and rows of bearing balls may be prohibitively expensive.
Additionally, the use of a single yaw bearing in a wind turbine may result in increased load peaks. This is because the loads that the yaw bearing is subjected to are reacted over concentrated areas of the bearing. Load peaking describes load distribution, such as between the various bearing balls of a bearing. A high load peak means that the load on the most highly loaded component, such as a bearing ball, is higher than the average load on all components. More efficient load transfer is thus obtained when load peaks are reduced. Thus, the yaw bearings of larger wind turbines must account for such increased load peaks, which can compound the impracticability and expense of the yaw bearing.
Accordingly, a wind turbine with an improved yaw bearing assembly would be desired in the art. For example, a yaw bearing assembly that provides improved distribution of loads would be advantageous.